When Judy and I first married it seemed like I was always retying her shoes for her. She’d tie them in the morning, then shortly after they’d come undone. I’d retie them and they’d stay tied. Never really made anything of that, I just had a talent for tying knots, until at some point years later, we realized that there was a problem with the knot Judy was tying. Tying shoes is simple. You tie an overhand knot, then you tie the loopy part on top of that. I had never thought about the logic of it, but the two knots have to interact; things have to be done in the right order. Knots are sensitive like that. A square knot is just two overhand knots tied one on top of the other. It’s a wonderfully simple and reliable knot. Get the second overhand knot backwards though and the square knot becomes useless; a slip knot. When Judy learned as a kid to tie her shoes, the subtlety of which loop goes around which was missed. Her shoe knot becomes a slip knot. When you learn something as a kid, and it becomes automatic, it’s hard to relearn it as an adult. Sometimes you even teach a kid to tie their shoes exactly as you learned to tie yours, and pass the problem along for another generation. Sorry Becky. This problem has been overcome at our house however. Judy no longer buys shoes with laces. She mostly wears sandals, but when she has to wear real shoes, she’ll only wear shoes with Velcro straps. This all comes to mind because lately I’ve noticed that every time I go for a walk, my left shoe comes untied sometime during that hour. How can that be? I’m the knot tier. My knots don’t come undone! I puzzled about it for a while and came up with a possible explanation. Our modern running shoes come with ample shoelaces. There is plenty of string to tie, with maybe even more than we really need, so that when walking or running there is so much shoelace flopping about it can brush against the other foot or leg and be a little distracting. That happened to me, but I figured out a way around it. I started tying the left shoe over on the left of center and the right shoe to the right of center. That keeps the shoelaces for one foot away from the shoe for the other foot. Problem solved, and a new one created at the same time. By tying my shoe off to the side, right against the edge of the shoe, I change the dynamics of the knot. One shoe is getting pressure to untie from the right and one from the left. Knots are sensitive like that. That shoe-tie knot is more susceptible to pressure from the left than from the right. The slight pressure from the left is enough to cause the knot on that side to loosen, while the one on the right remains unaffected. I returned to tying both shoes right in the middle of each foot, and theory confirmed. Both shoes now remain tied!